1. Field of the Invention
The present invention relates in general to accessories of an office machine, and more particularly to an automatic document feeder suitable for use with the office machine to separate a plurality of documents, set on a document feeding base of the office machine, one by one and to feed the separated document to the office machine.
2. Description of the Prior Art
Some of known office machines, such as a copying machine, a laser printer and a facsimile, is preferably equipped with an automatic document feeder (ADF) at its document feeding section. The ADF is adapted to automatically separate a plurality of documents one by one and to feed the separated document to the office machine, thereby improving the document processing performance of the office machine.
The ADF according to the prior art generally includes a document separating belt and a document separating roller which come into close contact with each other for separating the plurality of documents one by one and for feeding the separated document. Here, when separating the documents, the document separating roller is rotated while the document separating belt is not moved. Since the separating belt is not moved as aforementioned, a part of the separating belt comes into repeated contact with the rotating roller and is inevitably abraded, thereby shortening the using life of the belt and requiring to be often substituted with new one. Moreover, the abrasion of the document separating belt causes deterioration of the document separating and feeding performance of the ADF. Additionally, it is required to make the rotating separating roller come into direct contact with the fixed separating belt prior to introduction of the document to the nip between the separating roller and the separating belt, and this generates a remarkable frictional force between the belt and roller. The roller driving motor of the ADF is thus imparted with a remarkable load.
In an effort to solve the above problems, the applicant proposed an automatic document feeder in Korean U.M. Application No. 91-11586.
With reference to FIG. 1, there is shown in a perspective view the automatic document feeder of the above Korean U.M. application. This document feeder includes an endless document separating plane belt 13 which is rotatably supported by both a stationary belt roller 12 and a rotatable belt roller 15 and comes into close contact with a document separating roller 18. The rotatable roller 15 is supported by a rotating shaft 15a which is in turn provided at both ends thereof with individual larger diameter supports 16. Each of the supports 16 is in turn movably inserted in a slot 14a formed in each side wall of a rotation-side bracket 14. Hence, the rotatable roller 15 is rotated along with the rotating shaft 15a rotatably supported by the bracket 14. On the other hand, the stationary roller 12 is supported by a rectangular shaft 12a which extends from the opposite side ends of the roller 12 and is in turn inserted in a rectangular slot 11a, formed in each side wall of a stationary-side bracket 11, such that it is prevented from rotation. Here, the rotating shaft 15a is upwardly and backwardly biased by means of biasing means, such as a pair of tension coil springs 17 each connected between the rotating shaft 15a and an upper cover (not shown) of the document feeder main body. Thanking for the springs 17, the separating belt 13 always comes into close contact with the separating roller 18 with an appropriate tensile force.
However, the above document feeder, while somewhat lengthening the using life of the document separating belt 13 and improving the document separating and feeding performance of the document feeder, nevertheless has a problem caused by its complicated structure. Otherwise stated, the stationary-side bracket 11 and the rotational-side bracket 14 are separately mounted on the main body of the document feeder and, particularly, the rotation-side bracket 14 should be provided with the slot 14a for maintaining the desired tensile force of the document separating belt 13 using the springs 17. Moreover, the tension coil springs 17 are additionally connected to the upper cover of the main body. Hence, the problem of the above document feeder is resided in that it is difficult to manufacture and to assemble the feeder and to substitute a trouble element with new one.